The present invention generally relates to fuel-fired heating appliances and, in a representatively illustrated embodiment thereof, more particularly relates to a fuel-fired water heater having incorporated therein a specially designed draft inducer fan assembly that substantially reduces undesirable heat loss from the water heater during standby periods thereof, thereby desirably increasing the overall energy efficiency of the water heater.
In the area of fuel-fired water heaters a continuing design challenge is the reduction of heat loss from the water heater, which causes an undesirable lessening of the overall energy efficiency of the water heater, during idle or “standby” periods of the water heater. A substantial portion of the standby period heat loss from tank type water heaters occurs at the flue gas discharge area thereof. At such area, convective flows of flue-heated air rising from the water heater, or cold air downflows into the flue, can undesirably reduce the temperature of the tank-stored water, thereby correspondingly diminishing the overall energy efficiency of the water heater.
One conventionally utilized approach to lessening this flue discharge area heat loss is to place a motorized shutoff damper in the flue or in a discharge pipe connected thereto and control the damper in a manner such that it is motor-driven to an open position shortly prior to and during draft inducer fan operation and motor-driven to a closed position during idle periods of the fan corresponding to standby periods of the water heater. However, in various water heater applications, such as in the residential market, this addition of a motorized damper and associated controls to the water heater can increase the production cost of the water heater to an unacceptable extent.
From the foregoing it can be readily seen that a need exists for improved apparatus for lessening the flue gas discharge area heat loss of a fuel-fired water heater during standby periods thereof. It is to this need that the present invention is directed.